The present invention relates to an image forming apparatus which detects a stained portion of a charging wire by detecting an undesirably made white line (hereinafter merely referred to as a white line) in a formed image and cleans the charging wire at the stained portion.
Generally, image forming apparatuses such as a copying machine experience undesirable adhesion of particles to a charging wire. These particles include flying toner which is toner which is residual on the surface of a photosensitive drum after an image transfer operation and is not cleaned by a cleaning device, dust entered into the image forming apparatus, and paper powders coming off from copying sheets. In this case, a charger cannot apply a voltage of a specified level to the photosensitive drum and a white line appears in a formed image over a sub-scanning direction thereof. Conventionally, when this occurs, the charger is removed from the image forming apparatus and is cleaned carefully at a portion corresponding to the white line found on the copy sheet. Such a work has been very cumbersome. Accordingly, there has been recently proposed an image forming apparatus provided with a charging wire cleaning mechanism. Specifically, a cleaning pad is provided in a charger to clean a charging wire. This cleaning pad slides along the charging wire to clean the stains such as toner and paper powders adhered to the charging wire.
In the image forming apparatus provided with the charging wire cleaning mechanism, the charging wire is cleaned during a period which lasts until the apparatus brought into a steady state after the apparatus is started by turning on a main switch (a period which lasts until an image forming operation is permitted after the start-up of the apparatus). The arrangement is such that the cleaning pad makes one back-and-forth sliding movement along the charging wire in a main scanning direction at a constant speed while being held in contact with the charging wire. However, this is not sufficient sometimes to clean off the stains such as the adhered toner completely. In order to overcome this problem, the cleaning pad may be arranged to move back and forth along the charging wire plurality of times. This inadvertently causes an in a cleaning time or faster abrasion of the cleaning pad, and thus may not be an efficient way.